Plan the pond around two sets of typical planning figures: a deep, calm refuge of roughly 120 to 150 centimetres where an aging koi can rest through winter cold and summer heat, and broad sloping ledges about 30 and 60 centimetres below the surface, each at least 60 centimetres wide. These figures are typical planning ranges for a temperate garden pond rather than a rule for every climate, and colder regions may call for a deeper refuge still. What matters is the shape they create together: an old fish can sink into stable, quiet water when weather turns harsh, or rise onto a shelf and rest in the shallows without swimming against flow to hold its place, choosing its depth through the day with very little effort.
The Deep Refuge: Depth, Calm and Stability
Give the refuge more depth than anywhere else in the pond, typically in that 120 to 150 centimetre band, and place it away from waterfalls, returns and aerator plumes that stir the bottom water. Deep water changes temperature slowly, so the refuge stays cooler during a hot spell and remains the last part of the pond to chill in winter, giving an aging fish a stable resting zone in both extremes. Keep the refuge floor smooth and clear of rocks, plant baskets and pipework that an old fish resting low could scrape against or become wedged beside. Avoid sudden drop-offs at the refuge edge; a firm, gradual slope lets a stiff, slow fish move in and out without a scramble. Size the refuge for the whole group rather than for one fish, since koi rest together and crowding in a small deep pit defeats its calm.
Ledges an Old Fish Can Actually Rest On
Build ledges as broad shelves, each at least 60 centimetres wide, at roughly 30 centimetres and again at roughly 60 centimetres below the surface, joined by gentle slopes rather than steps with vertical faces. Width is what turns a shelf from a planting ledge into a resting place: a large old koi needs room to lie along the shelf without its tail hanging over the edge into deeper water. Keep shelf surfaces smooth and free of gravel traps, sharp stone edging and basket rims that press into a resting belly. Set planting back from at least part of each ledge so plants do not colonise the whole resting area, and leave the shelves in the quieter half of the pond, away from the skimmer draw and the main current. A resting ledge in gentle shade suits summer afternoons, while a ledge catching morning sun gives an old fish a warm shallow spot in spring and autumn, so spread ledges across two aspects of the pond where the shape allows.
Flow, Shade and Seasonal Comfort
Resting comfort fails when current crosses the shelves, so aim filter returns along walls or toward the deep zone, and test the flow with a few leaves or a scrap of food before judging a ledge calm. Provide shade over part of the shallow water with planting or a pergola edge, positioned so the pond keeps open sunlit water too, and remember that shade also slows the fierce summer warming that makes shallow ledges uncomfortable by afternoon. In winter, keep a small area of surface from sealing completely where your climate freezes, and avoid breaking ice with blows that send shock through the water where old fish rest below. Feed aging koi where they can reach food without competing in strong current, and watch which ledges each older fish chooses across the seasons, since their choices tell you where the pond still works hard against them. A pond reshaped this way asks very little swimming from a tired fish in any month. Pet Passport in KinsLe records each koi by age and past health notes in one packet, helping you match the pond's resting places to the fish growing old in it.